/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference, 2nd Edition"
 * by Nicolai M. Josuttis, Addison-Wesley, 2012
 *
 * (C) Copyright Nicolai M. Josuttis 2012.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include "algostuff.hpp"
using namespace std;

// function object to process the mean value
class MeanValue
{
private:
    long num;    // number of elements
    long sum;    // sum of all element values
public:
    // constructor
    MeanValue() : num(0), sum(0)
    {
    }

    // function call
    // - process one more element of the sequence
    void operator()(int elem)
    {
        num++;          // increment count
        sum += elem;    // add value
    }

    // return mean value (implicit type conversion)
    operator double()
    {
        return static_cast<double>(sum) / static_cast<double>(num);
    }
};

int main()
{
    vector<int> coll;
    INSERT_ELEMENTS(coll, 1, 8);
    // process and print mean value
    double mv = for_each(coll.begin(), coll.end(),   // range
                         MeanValue());              // operation
    cout << "mean value: " << mv << endl;
}
